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The drilling technology was developed to increase the drilling efficiency based on 3 basic reasons, i.e.: safety, minimum cost, and usable hole. Casing drilling is one of drilling technology which it has been applied in many oil fields in Indonesia. The casing drilling is classified into 3 methods, i.e.: Retractable Bit, Liner Drilling, and Drilling with Casing, where each method can be applied in certain condition. Recently, the drilling technology has reached efficiency significantly, both in engineering and economical aspects, especially in the formation which is difficult to drill with conventional drilling method, for examples:Abnormal/subnormal zoneThief/loss zoneUnstable formation Generally, the drilling efficiency can be formulated based on statistic trend from the field data. Thus, casing drilling can be developed to reach the drilling efficiency according to the field experiences. I. INTRODUCTION Many methods were developed in drilling operations as an effort to increase the efficiency of drilling operation, thus it can be reached less time, minimum cost, and the best result. One of the methods is casing drilling technology, which was considered to be solution for some drilling problems and also provide less time in drilling operation with penetrating and casing program do simultaneously in one trip, with the purposes as follow:To penetrate trouble zone and running casing safely and efficiently.Provide less time in drilling operations.Creating good and safety well construction for exploration and production steps.Minimize the cost with reducing rig downtime resulting from unexpected occurrences that generally occurred in conventional drilling operations.

This paper was prepared for presentation at the 1999 SPE International Symposium on Oilfield Chemistry held in Houston, Texas, 16-19 February 1999.

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In modeling the hydraulic fracking program for unconventional reservoir shales, information about elasticity rock properties is needed, namely Young's Modulus and Poisson's ratio as the basis for determining the formation depth interval with high brittleness. The elastic rock properties (Young's Modulus and Poisson's ratio) are a geomechanical parameters used to identify rock brittleness using core data (static data) and well log data (dynamic data). A common problem is that the core data is not available as the most reliable data, so well log data is used. The principle of measuring elastic rock properties in the rock mechanics lab is very different from measurements with well logs, where measurements in the lab are in high stresses / strains, low strain rates, and usually drained, while measurements in well logging use the principle of measured downhole by high frequency sonic. vibrations in conditions of very low stresses / strains, High strain rate, and Always undrained. For this reason, it is necessary to convert dynamic to static elastic rock properties (Poisson's ratio and Young's modulus) using empirical equations. The conversion of elastic rock properties (well logs) from dynamic to static using the empirical calculation method shows a significant shift in the value of Young's Modulus and Poisson's ratio, namely a shift from the ductile zone dominance to the dominant brittle zone. The conversion results were validated with the rock mechanical test results from the analog outcrop cores (static) showing that the results were sufficiently correlated based on the distribution range.